<html>
<head>
    <meta charset="UTF-8">
    <title>Index Document</title>
    <style>
    	.h {
    		background-color: red;
    	}

    	.bg {
    		color: white;
    	}
    </style>
	<script type="text/javascript" src="http://cdn.bootcss.com/jquery/2.2.4/jquery.min.js"></script>
    <script>
    	$(function() {

    		// do 1
    		// console.info($("#hello"));
    		// console.info(document.getElementById("hello"));
    		// $("#hello").addClass("h");
    		$("#hello").style("")
    	});

    	$(function () {
    		// do 2
    		console.info($("#world"));

    	});
    	
    </script>
</head>
<body>
    <h1 id="hello" class="h bg">
    	Hello
    </h1>
    <h1 id="world" style="display: none">
    	World
    </h1>


</body>
</html>